ATOMS
About 4.9% is ordinary
Planck found ordinary matter, the stuff of stars, planets and people, makes up only about 4.9% of the universe's mass and energy.
See the recipeWHAT THE MEASUREMENTS SAY
Only about 5%
is made of atoms.
Everything you can touch is the small part.
See the recipe
13.8 BNyears and counting
Stars, planets, oceans and people are all built from ordinary atoms. Space missions that mapped the universe's oldest light found that atoms make up only about 5% of it. The rest is dark matter and dark energy.
At a glance
- Atoms are the small part
- Dark matter holds galaxies
- Dark energy speeds it up
- A universe mostly unseen
13.8 bn years
Age of the universe
Planck put the age at 13.82 billion years. NASA's WMAP mission had found 13.77 billion years, to within half a percent.
AGE · PLANCK 2013
2.726 K
Temperature of the microwave background
ESA gives the background's temperature as 2.726 Kelvin, about -270°C, nearly everywhere on the sky.
OLDEST LIGHT · ESA
TWO NUMBERS WORTH KNOWING
Very old,
and very cold.
One figure for the universe's age,
one for the temperature of its oldest light.
The tiny differences in that glow, about 1 part in 100,000, were the seeds that later grew into galaxies and clusters of galaxies, according to ESA.
THE COSMIC RECIPE
What is the
universe made of?
Pick an ingredient to see its share of the universe's total mass and energy. The bar shows how big a slice it is.
Figures from the Planck mission results announced on 21 March 2013. Other missions give close but slightly different values.
THE SHORT ANSWER
Three ingredients,
one small slice.
The Planck mission's 2013 results gave the recipe.
Ordinary matter is the smallest part.
OLDEST LIGHT
A glow from the start
The cosmic microwave background was released when the universe was about 380,000 years old. Mapping it is how the recipe was measured.
See the numbers
EXPANSION
Growing, and speeding up
Expansion was confirmed in 1929. In 1998 two teams found it is speeding up, which is what dark energy names.
How we know
FOUR STEPS TO THE RECIPE
How a glow
became a census.
The cosmic recipe was not guessed. It came from a century of measurements, each building on the last.
1929: the universe is expanding
NASA notes that astronomers confirmed the universe was expanding in 1929, years before anyone could map its oldest light.
1965: a hiss from every direction
Testing a sensitive horn antenna at Bell Laboratories, two radio astronomers found microwave radiation matching a body at about 2.7 Kelvin.
1998: the expansion speeds up
Two teams watching faraway exploding stars found the expansion is accelerating. The finding won the 2011 Nobel Prize in Physics.
2001 to 2013: mapping the glow
NASA's WMAP, launched in 2001, and ESA's Planck, launched in 2009, mapped the background in fine detail and gave the recipe.
THE SHAPE OF SPACE
Flat, as far
as we can tell.
WMAP measured the curvature of space to within 0.4% of flat, the ordinary geometry of school maths, where parallel lines never meet.
The same maps gave the expansion rate. Planck's 2013 value was 67.15 km/s per megaparsec, and NASA says the speeding up began about 9 billion years after the universe began.
Questions
Questions people ask
How old is the universe?
About 13.8 billion years. The Planck mission's 2013 results gave 13.82 billion years, and NASA's WMAP mission found 13.77 billion years to within half a percent.
What is the cosmic microwave background?
It is the oldest light we can observe. ESA explains that about 380,000 years after the start, the universe had cooled to around 3000 Kelvin and became transparent, letting this light travel freely.
How much of the universe is dark matter?
Planck's 2013 results put dark matter at about 26.8% of the universe's mass and energy. NASA says it is thought to make up about 85% of all matter.
What is dark energy?
It is the name for whatever is causing the expansion of the universe to speed up. NASA says approximately 68.3 to 70% of the universe is dark energy.
Who discovered the leftover glow?
Two radio astronomers at Bell Laboratories found it in 1965 while testing a horn antenna. They were awarded the Nobel Prize in Physics in 1978.
Sources
Where the facts come from
- Max Planck Society: Planck reveals an almost perfect Universe (2013)
- ESA: Planck and the cosmic microwave background
- NASA Science: WMAP mission overview
- NASA Science: Dark Energy
- HyperPhysics (Georgia State University): Discovery of cosmic background radiation
- Nobel Prize: The Nobel Prize in Physics 2011, summary
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